GFS2: Fix address space from page function

Now that rgrps use the address space which is part of the super
block, we need to update gfs2_mapping2sbd() to take account of
that. The only way to do that easily is to use a different set
of address_space_operations for rgrps.

Reported-by: Abhi Das <adas@redhat.com>
Tested-by: Abhi Das <adas@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/meta_io.h b/fs/gfs2/meta_io.h
index 4823b93..ac5d802 100644
--- a/fs/gfs2/meta_io.h
+++ b/fs/gfs2/meta_io.h
@@ -38,12 +38,15 @@
 }
 
 extern const struct address_space_operations gfs2_meta_aops;
+extern const struct address_space_operations gfs2_rgrp_aops;
 
 static inline struct gfs2_sbd *gfs2_mapping2sbd(struct address_space *mapping)
 {
 	struct inode *inode = mapping->host;
 	if (mapping->a_ops == &gfs2_meta_aops)
 		return (((struct gfs2_glock *)mapping) - 1)->gl_sbd;
+	else if (mapping->a_ops == &gfs2_rgrp_aops)
+		return container_of(mapping, struct gfs2_sbd, sd_aspace);
 	else
 		return inode->i_sb->s_fs_info;
 }